Maybe you lost what I sent you a few days ago:
Home Depot/Lowe's/your local plumbing supply should have these. Very common.
11 Ts 1/2" - (1 bag of 10) + 1 loose.
4 end caps 1/2"
10' 1/2" CPVC - there will be some left over.
I think it was under $7 in total.
You can cut the slits with a Dremel, hack saw, radial arm saw, circular saw, etc. you don't want the kerf too wide. 1/16-3/32" works fine.
There's no advantage to go larger diameter than 1/2", it may not even fit as the Ts get larger with size.
The bulkhead part can be trickier, unless, as I posted before, you can fit a vinyl or silicone hose through the existing drain hole. I think it was 7/16" OD for vinyl, but 1/2" OD silicone may work if you have it, haven't tried that. It should just fit, like very tight. Then a drop of glue or silicone will seal it off if you feel the need. It may not be needed if it fits very tight; it creates its own seal. That would take a lot of work out of the conversion job, and you don't have to buy a bulkhead, saving $12+. Which means you can mash sooner.